Spark plug



C. H. DUFFY.

SPARK PLUG. APPLICATION FILED JUNE 21, 1918.

Patented Jan. 10, 1922.

PATENT OFFICZE.

CHARLES HUGH DUFFY, OF CHEVY CHASE, MARYLAND.

SPARK PLUG.

Specification of Letters Patent.

Patented Jan. 10, 1922.

Application filed June 21, 1918. Serial No. 241,199.

To all whom it may concern:

Be it known that I, CHARLES HUGH DUFFY, a-citizen of the United States, residing at Chevy Chase, in the county of Montgomery, State of Maryland, have invented certain new and useful Improvements in Spark Plu and I do declare the following to be a fu 1, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same, reference being had to the accompanying drawings, and to the letters and figures of reference marked thereon, which form a part of this specification.

This invention relates to spark-plugs of the composite insulation type but more particularly to spark-plugs in which a mica core is employed as the outer exposed portion of the insulation, and in which an inner end or portion of porcelain, lava or preferably quartz or similar material is used.

Spark-plugs constructed in accordance with this invention are particularly applicable for use on airplane motors, wherein conditions are particularly severe and themaximum of dependability is essential.

In spark-plugs wherein a one-piece insulator of porcelain, lava, quartz or similar material is employed, a critical line exists at the outer shoulder of the piece, at which there is at all times present the possibility and likelihood of a fracture, while in mica insulators exposed to the products of combustion of a motor, there is present a capillary action between the mica washers of the core, causing the core to take in or absorb oil. It is thus seen that mica presents a decided disadvantage when in direct communication with the combustion chamber of the motor, but a decided advantage when employed as an insulation on the outside of the plug. On the other hand a homo eneous non-porous material such as porce ain or preferably quartz is decidedly preferable as an insulation directly subjected to the products of combustion, but disadvantageous as an insulation extending outside of the plug.

To provide an insulation wherein the disadvantages of these insulations are eliminated and the insulating and mechanical characteristics are employed to the fullest extent, I provide that part or portion of the insulation which extends beyond-the shell, of mica, and that portion of the insulation which is subjected to the products of combustion, of porcelain, lava, quartz or similar material.

This invention consists in th novel construction and arrangement of the insulating members, the means employed for mounting the members, and in the method of retaining the members within the spark-plug gland and of seating the same within the sparkph ig shell.

he invention also consists in the novel construction of the ground electrode of the spark-plug and in the method of permanently securingand retaining the same in proper efi'ective position against casual displacement.

Referring to the accompanying drawing:

Fig. 1, is a vertical sectional view of a spark-plug constructed in accordance with this invention.

Fig. 2, is an elevation of the same.

Fig. 3, is a view partly in vertical section, and partly in elevation illustrating the plug in inverted position as in assembling the same.

Fig. 4, is an elevation of mica core illustrating mica washers on central metal spindle before the mica is machined, the finished machined core being illustrated or indicated in dotted lines. In this figure are also represented in dotted lines, the novel constructions of the plug insulation.

Fi 5, is an elevation of the spun gland and insulation as a unit, and

Fig. 6, is an elevation of the insulation-retaining gland in its initial condition.

Like numerals of reference indicate the same parts throughout the several figures, in which 1 indicates the spark-plug, including thehollow metal shell 2, having the usual threaded end for connection with a motor, the mica core insulation section 3 made up of mica washers 4 disposed around an inner wrapped or wound section of mica 16 mount ed on a threaded metal spindle 26. The

said spindle 26 includes a head 27 and a follower member 24, between which the mica washers 4 are tightly compressed; a nut 25 threaded on the spindle 26 retains the mica washers in proper effective position.

I In Fig. 4, the mica core washers are illustrated laminated on the spindle in condition before the core is machined, and any proper formation can be given the core by machining. It is usual to form the mica core and leave the head 27 thereon as shown in full lines in Fig. 4, the particular form and size of the head being varied according to the design of the plug. As distinguishing my construction from this practice, attention is directed to the elements shown in dotted lines in said Fig. 4. It will be observed that I continue the spindle 26 down below the spindle head 27 to form the electrode-member 9, which receives the electrode 10, upon which electrode-member 9 is mounted the inner insulating end or member 5 of porcelain, quartz or the like, said member 5 being centrally bored at 29, (Fig. 1) to freely receive said electrode member 9 and its electrode 10. This mounting of the insulating member 5 insures an exact centering and alinement of the two insulating members 3 and 5 and allows easy provision against gas-leakage by interposing a soft (preferably copper) gasket 19 between the spindle-head 27 and the face 13 of the insulating member 5.

Referring now to the shell 2 and gland 14, it will be seen that the latter is provided with a threaded section 15 for threaded connection with the shell 2, said gland being provided with a shoulder complemental to the shoulder 7 at the upper extremity of the enlarged central portion 8 of the mica core 3. The gland 14 is bored to receive the mica core 3, and includes a thin depending readily distortable tubular portion 12. The shell 2 is provided with a shoulder 17 disposed in the path of inward progression of the tubular portion 12, the angle of said shoulder 17 being complemental to the tapered or angular portion 11 of the inner insulating member 5.

.Beferrin now to the ground electrode 20, it will be 0 served that the same is received within a hole 21 formed in the end of the shell 2, and it will be seen that said hole is crossed or intersected by a hole or bore 22 transversely of the shell 2, said transverse hole 22 forming a pocket 30 behind the electrode 20. In afiixing the electrode 20, the same is inserted in the hole 21, and when in final position, a punch or-similar implement is inserted in the hole 22, and that portion of the electrode 20 within the hole 22 is driven, bent or distorted into the pocket 30, as indicated b the loop 23. The electrode 20 thus afiixe is permanently retained in the shell against displacement or rotation.

The method of assembling the plug is as follows:

The parts are inverted as shown in Fig. 3. A thin tube or wrapping of mica 16 is inserted within the gland 14, the mica core 3 positioned therein, the gasket 19 is placed against the head 27, and the inner insulating end or member 5 is slipped over the electrode-member 9, a suitable gasket 18 is positioned on the insulating member 5 (Fig.

3), and the shell 2 is then threaded down on the gland l4. Thisrelative movement of the shell and gland causes the thin readily distortable portion 12 of the gland 14. to engage the shoulder 17 in the shell 2 and be spun on said shoulder 17 and over and around the gasket 18 and insulating member 5, thus creating a gas-tight union between the spun end 28 (Fig. 1) of the gland and between the gland and the insulating member 5. As the gland 14 reaches its limit I of inward progression within the shell 2,. the mica core-head 27 is forced against the gasket 19 on the face 13 of the insulating member 5, compressing said gasket and effecting a gas-tight C1ioint between these parts. It has been foun that the presence of the mica core 3, provides an elastic backing for the lower insulating member 5, somewhat different in function from that of a hard, rigid, homogeneous insulating member. The effect of this elastic backing provided by the mica core 3 is to relieve the lower insulating member 5 from excessive mechanical strains, and at the same time compensate for the linear expansion of the metal shell and gland, to such extent that the plug will be maintained gas-tight under extreme variations in temperature.

The foregoing construction and method of mounting the insulating members combine the insulating members and gland in a single unit, so that the insulation and gland are demountable as a unitary member as illustrated in Fig. 5; while upon re-assembly the initial seating of the parts and a permanent gas-tight structure are assured.

In a simple and an efiicient manner the proper disposition of the mica and porce-. lain or quartz insulating members is effected to the end that the superior characteristics of each are fully utilized, while each is denuded of influences which normally impair proper functioning and result in their partial or complete breakdown.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. A spark-plug including a metal shell threaded for connection with a motor, said shell being internally chambered and, provided with atapered shoulder and threaded for connection with a core-retaining gland,

a core-retaining gland threaded for connection with said shell, internally chambered, provided with an internal shoulder and a thin depending readily distortable portion, an insulation including a mica core shouldered complementally to the shoulder in the gland and including a metal spindle having a head and means for retaining the mica forming the core on said spindle and snugly against the spindle-head, the said spindle including a depending electrode-member in continuation thereof and below the said spindle-head, said insulation including a homogeneous insulating member centrally bored to freely receive said depending electrode-member and provided with a tapered shouldered portion, the said depending readily distortable portion of the gland being disposed over and upon the tapered shouldered portion of the homogeneous insulating member and between the same and the said shoulder in the shell.

2. A spark-plug including a shell internally chambered and having an internal shoulder and threaded for connection with a core-retaining gland, a core-retaining gland threaded for connection with the shell, a mica core including a metal spindle, itself having a spindle-head and means for retaining the mica of the core on the spindle and snugly against the spindle head, said spindle including a depending electrode-member in continuation thereof and below the electrode head, and a homogeneous insulating member centrally bored to freely receive the depending electrode-member and externally formed to conform to the shoulder in the said shell, said gland having a portion surrounding the said homogeneous member between the same and the metal shell to impart uniform rotation to the homogeneous member with the mica core and spindle, upon rotation of the gland.

3. A spark-plug including a shell, a mica core itself including ametal spindle having a spindle head andmeans for retaining the mica of the core on said spindle and snugly against the spindle-head, said spindle having in continuation thereof an electrodemember below the spindle-head, a homogeneous insulating member on said electrode-member and faced to conform to the said spindle-head, and rotatable means for retaining the said mica core and its spindlehead snugly upon said homogeneous insulating member within the shell, said last mentioned means being in engagement with both the mica core and the homogeneous member to impart rotation to the homogeneous member uniformly withthe mica core and spin-' dle, upon rotation of the said rotatable means.

4. A spark-plug including a shell, a mica core itself including a metal spindle having a spindle-head and means for retaining the mica of the core on thespindle and snugly against the spindle-head, a homogeneous insulating member below the mica core andits spindle-head, and means encompassing both the mica core and the homogeneous member forretaining' the mica core and its spindle-head snugly upon the said homogeneous insulating member within the shell.

5. In a spark-plug, a mica core including a metal spindle and spindle-head, said spindle being continued below the spindle-head, and a homogeneous insulating member received on the said continued portion of the mica core and a homogeneous insulating member, the said homogeneous insulating member being mounted on the spindle of the mica core and below the spindle-head of the mica core, and means for exerting pressure on the mica core to snugly hold the homogeneous insulating member between the spark-plug shell and the spindle-head, said means including an element surrounding the homogeneous member for retaining the homogeneous member and mica core against relative movement.

7 A spark plug including a shell, two insulating members, one above the other and separated by a metal flange, a packing gasket under the lower insulating member, and means rotatable in said shell and surrounding and encompassing said two insulating members and the packing gasket for holding said two insulating members and packing gasket against relative rotation with respect to one another and with respect to the rotatable means.

8. A spark-plug including a shell, a spindle, a mica core on said spindle, a homogeneous insulating member under said mica core, a packing gasket under the homogeneous member, and means rotatable in said shell and surrounding and encompassing said mica core, homogeneous insulating member and packing gasket for holding the same against rotation relative to one another and against rotation relative to the rotatable means.

9. A spark-plug including a mica core having a metal spindle and spindle-head and means for retaining the mica of the core on the spindle and snugly against the spindlehead, said spindle being continued below the spindle-head, a homogeneous insulating member mounted on the continued portion of the spindle, means in the spark-plug shell onwhich the homogeneous member is positioned, and means for pressing the mica core and spindle-head inwardly of the shell and upon the homogeneous insulating member to effect a gas-tight joint between the spindle-head and the homogeneous insulating member, said last mentioned means including an element for connecting the mication extending within the said pocket and out of line with the aligning straight portions thereof lying in the first mentioned hole above and below thetransverse hole.

11. A spark plug including a shell provided with a hole to receive an electrode, and provided with a pocket in communication with said hole at a point intermediate the ends of said hole, an electrode in said hole and having aligning straight portions above and below said pocket, said electrode including a bent portion extending within the said pocket and out of line with the aligning straight portions of the electrode in said hole above and below the said pocket.

-12. The herein described method of seating and retaining the insulation and central electrode in a spark-plug shell, which consists in positioning a flanged central electrode between two insulating members, in disposing said central electrode and insulating members within a readily distortable spark-plug gland, in progressing said gland against a shoulder in the spark-plug shell to distort said gland and spin the same between the insulation and the said shoulder and to compress the said flanged central electrode between the said two insulating members.

13. The herein described method of seating and retaining the insulation and central electrode in a spark-plug shell, which consists in positioning the central electrode be tween two insulating members, in disposing said insulating members and central elec trode within a readily distortable sparkplug gland, in progressing said gland against a shoulder within said shell to distort said gland and spin the same between the said shoulder and the insulation, and to compress the said central electrode between the said two insulating members.

14. The herein described method of simultaneously effecting a gas-tight joint between the central electrode of a spark-plug and the insulation, and between the insulation and the spark-plug shell, which consists in posi-.

tioning a flanged central electrode between two. insulating members, in disposing the central electrode and insulating members within a readily distortable gland, in relatively progressing the gland against a shoulder in the spark-plug shell, and in spinning the gland between said shoulder and the insulation to compress the said flanged electrode between the two insulating members.

15. The herein described method of retaining a central electrode and insulation within the gland, and in spinning the distortable gland under the insulation.

17. The herein described'method of retaining and seating the central electrode and v insulation in a spark-plug shell, which consists in disposing a flanged central electrode between the contiguous ends of two insulating members, in positioning said central electrode and insulating members in a readily distortable gland, and in spinning the readily distortable gland under the insulation.

18. A spark plug including an internally threaded shell, a gland threaded for connection with the shell and including a thin tubular portion integral with the gland, an insulation including a mica core in said gland and a homogeneous insulating member under said mica core and surrounded by said gland, a packing gasket under the homogeneous insulating member, the said gland having a spun portion under and against said packing gasket on the homogeneous insulating member to hold said packing gasket, homogeneous member and mica core against rotation with respect to the said gland, and against relative rotation with respect to one another, upon threading the said gland into the said shell as in seating the insulation therein.

19. A spark plug including an internally threaded shell, a gland threaded for connection with the shell and including a thin tubular portion integral with the gland, an insulation including two insulating members-in said gland and surrounded thereby, the upper of said insulating members being laminated, the said gland having a spun portion under the lowermost of said insulating members to hold said members against rotation with respect to the said gland and against rotation with respect to each other, upon threading the said gland into the said shell as in seating the insulation therein.

In testimony whereof, I aflix my signature in presence of a witness. a

CHARLES HUGH DUFFY. Witness:

INEz T. WALDEN. 

